The Northcentral and the Midwest Chapters of the American Association of Physicists in Medicine, sponsored by the parent national organization (the AAPM), has planned, organized and will conduct a 3 1/2 day conference on "Prediction of Response in Radiation Therapy: Radiosensitivity and Repopulation". The symposium will provide an update on the current status of the biological, physical, clinical and modeling aspects of time, dose and fractionation schemes in radiation therapy. The invited faculty and other participating speakers will present the progress in predictive assays, (Tpot by flow cytometry and measurements of intrinsic radioresistance); advances in time factors and dose escalation strategies; modifiers of response analytical models and modeling techniques; concepts and methods of modern data analysis. A session will also be devoted to the new fractionation schedules in practice. The relevance of the above to clinical procedures will be emphasized. Evening workshops will provide tutorials in the basics, as well as providing a forum for discussion and identification of issues needing further investigation.